Firefox defaults to state 3: we don’t know what the user wants, so
we’re not sending any signals to servers. This causes the presence
of the signal to mean more — the signal being sent should be the
user’s choice, not ours. Therefore, Firefox doesn’t broadcast
anything until our user has told us what to send.

DNT allows for a conversation between the person sitting behind
the keyboard and the site that they want to visit. If DNT is on by
default, it’s not a conversation. For DNT to be effective, it must
actually represent the user’s voice.

That’s a bogus argument. If they really feel this way, then Firefox should present a modal dialog that forces every user to choose a Do Not Track setting before they can do anything else. Nobody likes those sort of dialogs, of course. People launch Firefox because they want to browse the web, not to fiddle with settings. That’s why default preference settings matter so much — everyone knows most users never change the defaults.

If “Do Not Track” defaults to on, most users will have it on; if it defaults to off, most users will have it off. Defaulting to off is no more a representation of “the user’s voice” than defaulting to on is.

The simple truth is that Mozilla is favoring advertisers (read: Google) at the expense of users’ privacy.